Cylindrical tube antenna with matching transmission line



g- 1966 J. D. WALDEN 3,26

CYLINDRICAL TUBE ANTENNA WITH MATCHING TRANSMISSION LINE Filed April 25, 1964 F/gz 2 H9. 3

INVENTOR J IMEs H WQuu-w ATTORNEYS United States Patent 3,268,899 CYLHNDRICAL TUBE ANTENNA WITH MATCHHNG TRANSMISSION iLllNE .l'ames ll). Walden, 714 Woodrow, Apt. 15, Houston, Tex. Filed Apr. 23, 1964, Ser. No. 361,948 2 Claims. (Cl. 343-741) This application is a continuation-in-part of my application Serial No. 189,808, filed April 24, 1962, now abandoned and entitled Antenna. Besides incorporation hereinto of the subject matter thereof, this present application also incorporates the subject matter of my corresponding application filed in Switzerland, April 23, 1963, No. 5,088,163.

This invention relates to electromagnetic radiation signal transducers such as antennas, and more particularly, to an expensive, simple antenna using a cylindrical tube in combination with a tapered impedance matching transmission line. The antenna of this invention is mainly designed for use with receiving sets, particularly, television and FM receivers; however, it should be appreciated that the antenna is also useful for other frequencies, as well as for transmission purposes, as desired.

The television art has heretofore developed antennas of complex and complicated structure and characteristics in order to give high gain over wide ranges of frequencies. Antennas have been developed which are known as all-channel antennas, and in addition, specialized antennas have been developed to be resonant at frequencies for certain channels within the television bands; however, there has been no good, inexpensive antenna developed for all channel use including color television reception which can be used to receive signals transmitted from beyond the line of sight, giving the same performance as the much more expensive antennas, for example the Yagi type. Of course, any reference to an antenna which will cover the television channels, will also cover FM radio bands, since such is in the midst thereof.

In my prior application above mentioned, a similar type antenna was set forth, and the present application extends the concept therein, and which is related herein also, to details for improving reception.

It is therefore the primary object of this invention to provide an improved antenna by which it is possible to receive both long range and local signals with a broad band effect regardless of whether the signals are in the AM, FM, or television ranges.

It is a further object of this invention to provide an antenna that can be manufactured inexpensively and simply, by using a tapered, impedance matching transmission line and metallic tubing, together with a suport. p Further objects and advantages of this invention will become more apparent to those of ordinary skill in the art upon reading the appended claims and the following detailed description, in connection with the diagrammatic drawings, in which:

FIGURE 1 is a front elevational view of the antenna;

FIGURE 2 is a plan View thereof; and

FIGURE 3 is a side elevational view of the antenna of FIGURE 1.

The main element of the antenna is the radiating cylindrical tube 10. To the opposite ends of this tube, as at points 12, there are respectively secured the end sections 14 and 16 of a twin or two-wire transmission or feed line 18. The tube and end sections 14 and 16 are in the same plane as apparent from FIGURE 3. These end sections diverge at an angle beta (5) from a converged point 20, from whence the two-wire transmission line extends downwardly to a receiver (not shown) in normal fashion. Of course, the transmission line or lead-in may be coaxial cable, if desired.

3,268,399 Patented August 23, 1966 A support or mast 22 is secured to the midpoint of tube 10 as by a U-bolt 24, and at the lower end of the antenna the transmission line 18 is secured to the mast by a block 26 which has protruding eyelets 28 or the like through which the two wires of the transmission line respectively extend. As indicated by the arrows, block 26 and eyelet 28 are movable up and down along mast 22, thereby tuning the antenna by varying the angle beta and effecting a desired impedance match with the receiver to which the antenna is connected.

It has been determined that tubing 11), which is preferably aluminum, must have an outer diameter in the range of from approximately one inch to one and onehalf inches, preferably one and one-fourth inches. Beyond the outer bounds of this range, the response of the antenna falls rapidly. It has also been determined that the length of tubing 10 should be a quarter wave length, though it can be /2 wave length, or any other multiple of A wave length, electrically speaking relative to a desired frequency of a given range, for example the center frequency thereof.

Tapered transmission line end sections 14 and 16 perform the function of matching the impedance of the tubing to the lead-in Wires from the antenna set, and they also provide, in conjunction with tube 10, the necessary inductance and capacitance so that the tubing member effectively has the required capacitance and inductance to act as a quarter-wave resonant member. The relatively large diameter of tubing 10 acts. to give the antenna system a low Q or broad-band response.

It has further been determined that the end sections 14- and 16 of the tapered transmission line should be stranded copper and not solid wires. The reason for this is not fully understood, but in any event solid wires reduce reception, apparently because they reduce the resonance of the antenna system to the operating frequency. These same points are true for the size of the end sections 14 and 16. That is, it has been determined that the diameter thereof should be equal to a standard AWG 20 stranded copper wire, 1 two grades; in other words, the diameter of end sections 14 and 16 should be of a gauge in the range of from 18-22. Outside of this range resonance is substantially reduced, as is reception.

With such a stranded wire tapered transmission line, it has been discovered that if ahuninum tube 10 is in the range of from 47 /2 inches to 48 /2 inches in length, reception appears to be best. This is particularly true when the angle beta is in the range of from 50 to preferably between 57 /2 to 62 /2 The angle may be varied by changing the vertical position of block 26 and eyelets 28, though it can also, or instead, be varied by changing the separation of the lower ends of sections 14 and 16 at point 20, for example between /8 inch to /2 inch, inch being preferred.

The antenna system with its specific dimensions above set forth provides the proper amount of capacitance and inductance to permit a one-quarter standing wave to exist on tube 10. Because of the low Q imparted by the diameter of the tubing, the one-quarter standing wave exists on the tubing in the VHF band, without excessive attenuation. A change in the angle beta tunes the onequarter standing wave to an optimum for the tubing at any desired frequency. This is generally not necessary, however, in the VHF band because of the low Q of the system.

While the theory of the efficient operation of the antenna is not fully understood, it is believed to be based on Clerk Maxwells formulation for the velocity of light whereby substituting the inductance and capacitance of a) the antenna system into the formula provides a broad band directional resonant frequency f equal to for frequencies in the kilocycle and megacycle ranges. Accordingly, the proper combination of the tubing and impedance matching tapered transmission line provides a sensitive antenna with a gain favorably comparable to the most complicated folded dipole stacked area antenna systems. It should be noted that reception by the antenna of this invention may be from. either side of tube 10, thereby causing the antenna to be directional broadly, but reception drops off when the signal approaches the antenna in the direction of either end thereof.

It is therefore apparent that this invention has provided an antenna which will provide reception with exceptional quality and high, broad band gain from AM, PM, or television electromagnetic radiation direct or via the upper atmosphere, for long or local range reception. The objects and advantages herein mentioned are therefore provided for, but other objects and advantages, and even further modifications of the invention, will become apparent to those of ordinary skill in the art upon reading this disclosure. However, it is to be understood that this disclosure is exemplary, and not limitative, the scope of the invention being defined by the appended claims.

What is claimed is:

1. An antenna comprising a cylindrical metallic tube having two outer ends and a length equal to approximately one-half of the Wave length of the near middle frequency of a desired band of frequencies and a diameter equal to approximately one inch, a two-wire transmission line having diverging end sections that are approximately equal in length to one-half of the wave length of the near middle frequency of the desired band of frequencies, each of the end sections of the transmission line being connected at one end respectively to one of the outer ends of the cylindrical metallic tube.

2. An antenna comprising a cylindrical metallic tube having two outer ends and a length equal to approximately one-half of the wave length of the near middle frequency of a desired band of frequencies and a diameter equal to approximately one inch, a two-wire transmission line having diverging end sections that are approximately equal in length to one-half of the wave length of the near middle frequency of the desired band of frequencies, each of the end sections of the transmission line being connected at one end respectively to one of the outer ends of the cylindrical metallic tubing, the transmission line being placed opposite the middle of the cylindrical metallic tubing at a distance so as to make the end sections of the transmission line rigid, and a support to hold the transmission line opposite the middle of the cylindrical metallic tube.

References Cited by the Examiner UNITED STATES PATENTS 2,631,235 3/1953 Sheriff 343803 X 2,657,311 10/ 1953 Kleis 343-822 2,878,473 3/1959 Perkins 343-866 2,972,146 2/ 1961 Saxe 343803 X FOREIGN PATENTS 515,853 12/ 1939 Great Britain.

692,692 6/ 1953 Great Britain.

715,460 9/ 1954 Great Britain.

OTHER REFERENCES Radio Research Laboratory: Very High Frequency Techniques, vol. I, first edition, pages 2 and 3, McGraw-Hill, 1947.

References Cited by the Applicant UNITED STATES PATENTS 2,131,108 9/1938 Lindenblad. 2,173,363 .10/1939 Roberts.

OTHER REFERENCES Jasik, Antenna Engineering Handbook, McGraw-Hill, pages 31 through 3-9 relied upon, 9 pages.

Noll et al., T.V. and FM. Antenna Guide, Macmillan Co., New York, page 221 relied upon, copyright 1951.

HERMAN KARL SAALBACH, Primary Examiner.

E. LIEBERMAN, Assistant Examiner. 

1. AN ANTENNA COMPRISING A CYLINDRICAL METALLIC TUBE HAVING TWO OUTER ENDS AND A LENGTH EQUAL TO APPROXIMATELY ONE-HALF OF THE WAVE LENGTH OF THE NEAR MIDDLE FREQUENCY OF A DESIRED BAND OF FREQUENCIES AND A DIAMETER EQUAL TO APPROXIMATELY ONE INCH, A TWO-WIRE TRANSMISSION LINE HAVING DIVERGING END SECTIONS THAT ARE APPROXIMATELY EQUAL IN LENGTH OF ONE-HALF OF THE WAVE LENGTH OF THE NEAR MIDDLE FREQUENCY OF THE DESIRED BAND OF FREQUENCIES, EACH OF THE END SECTIONS OF THE TRANSMISSION LINE BEING CONNECTED AT ONE END RESPECTIVELY TO ONE OF THE OUTER ENDS OF THE CYLINDRICAL METALLIC TUBE. 